1. Field of the Invention
The present invention relates to an improved apparatus and method for treating wood structures to arrest decay over extended periods of time. More particularly, the present invention relates to a method for packaging, dispensing, and safely introducing wood-protecting chemicals into the internal structure of wood.
2. Background of the Invention
Wood structures, particularly outdoor structures and supports, such as utility poles, piling supports, marine piles, and building components are subject to attack by wood-destroying fungi and insects. Often, such destruction can be ongoing and extensive internally before it is noticed externally.
One way to combat such destruction is to apply chemical(s) to the wood, preferably internally, which are toxic to these wood-destroying fungi and insects. Unfortunately, chemicals that are toxic to wood-destroying agents also are sometimes toxic to man, animals, plants, other insects, and to the environment, generally. Therefore, the release of such toxic agents into the wood structure must be carefully controlled and contained. Also, persons who are required to handle such chemicals may be in danger if they are not adequately protected during handling.
Effective protection of a wood structure will result only if the wood is treated over a long period of time: however, once a treatment is applied, it is nearly impossible co provide prolonged supervision of the treated structure. Therefore, the treatment should be inconspicuous so that children or animals do not tamper with the treatment, exposing themselves and others to potentially toxic chemicals.
Until recently, wood was treated with toxic chemicals by inserting enclosed packages of such chemicals into a preformed cavity in the wood. The chemicals were released by mechanical means, e.g., external mechanical pressure or for example, when the package contacted a puncturing device at the far end of the cavity. Another means for mechanically releasing such chemicals was to provide the chemicals in a cartridge which could be knocked into the wood using sufficient force to overpressure the cartridge and cause the chemicals to be injected into the wood. The shattering technique added the risk that shattered pieces of the cartridge might harm the person who was applying the cartridge, or otherwise harm the surrounding environment and its inhabitants.
One method used to minimize the foregoing risks was to use a container which permits a time-delayed release of the chemicals. Typically, time-delayed release involves the use of a container with at least a portion that will dissolve after a period of time. For example, a container may have a plug that is impermeable to the chemicals in the container, but chemically reactive so that the plug dissolves after a period of time. Alternately, the chemicals can be in a permeable package inside of an impermeable but chemically reactive outer container which dissolves after a period of time.
Time-delayed application of wood-treatment chemicals is safer than previous methods. Unfortunately, time-delayed application typically has a relatively short duration because, once the chemically reactive portion of the fumigant container dissolves, the release of the chemicals is substantially uncontrolled. As a result, the chemicals tend to dissipate more rapidly than desired.
U.S. patents of interest include, for example, Fahlstrom, U.S. Pat. No. 4,344,250; Hobbs, U.S. Pat. No. 5,244,615; Blom, et al., U.S. Pat. No. 4,389,446; Hollister, U.S. Pat. No. 1,999,458; Imus, U.S. Pat. No. 2,923,039; Loft, et al., U.S. Pat. No. 3,745,057; Errede, et al., U.S. Pat. No. 4,207,705; Baker, et al., U.S. Pat. No. 4,445,641; Amick, U.S. Pat. No. 4,552,752; Allan, et al., U.S. Pat. No. 4,554,155; Frimel, et al., U.S. Pat. No. 4,597,218; Drake, U.S. Pat. No. 4,793,474; and Frimel, et al., U.S. Pat. No. 4,932,155.
Other patents of interest include, House, Japan 4070972, filed Jun. 7, 1979; Shemeisu, Japan 7050901, filed Mar. 25, 1982; Heinen, Great Britain 848,122, filed Sep. 14, 1960; Freyberg, European Patent 131,759, filed Jan. 23, 1985; and Ghys. Australia 221,947, filed Jul. 27, 1958.
All references, articles, patents, patent applications, standards, and the like cited herein are incorporated by reference in their entirety.
A safe method to prevent wood decay using the long-term controlled release of wood-treating chemicals would be highly desirable. The present invention provides such a method.